In rice, basic unit of inflorescence is spikelet and each spikelet consists two rudimentary glumes, two sterile lemmas, and one fertile floret. The rice floret contains two bract-like structures (a lemma and a palea) hypothesized to be whorl-1 organs, two fleshy organs (lodicules) considered to be equivalent to eudicot petals, six stamens (whorl 3), and one pistil (whorl 4). In ABCDE model of rice flower development, many BCDE genes exhibit conserved or semi-conserved function in flower morphogenesis; however, A-class and E-class genes have novel functions in flower development compared to Arabidopsis. Rice genome contains five SEP-like genes, OsMADS1/LEAFY HULL STERILE1 (LHS1), OsMADS5, OsMADS7, OsMADS8, and OsMADS34 and knockdown of four of them, i.e. OsMADS1, OsMADS5, OsMADS7, and OsMADS8 resulted in the homeotic transformation of all floral organs into leaf-like organs with the exception of lemma, indicated SEP-like genes play a conserved role of ??E??function in specifying floral determinacy and organ identities (Cui et al., 2010). Developmental regulation of all floral whorls and meristem fate specification is accomplished by the interaction between OsMADS1 and OsMADS6 (Ohmori et al., 2009; Li et al., 2010, 2011a), and the direct repression of OsMADS34 expression by OsMADS1 mediates the spikelet-to-floret meristem transition, meristem maintenance, determinacy, and lateral organ development through multiple signaling pathways (Khanday et al., 2013). Interactions of OsMADS1 with OsMADS16 (a B-class gene), OsMADS3, OsMADS58 (C-class genes), and OsMADS13 (a D-class gene), respectively, and diversified regulatory functions of OsMADS1 and OsMADS6 play important role in specifying rice floral organ and meristem identity (Hu et al., 2015).
